function   get_week($date){
        $date_str=date("Y-m-d",strtotime('+5 day',strtotime('2017-10-26')));
    
        //封装成数组
        $arr=explode("-", $date_str);
         
        //参数赋值
        //年
        $year=$arr[0];
         
        //月，输出2位整型，不够2位右对齐
        $month=sprintf('%02d',$arr[1]);
         
        //日，输出2位整型，不够2位右对齐
        $day=sprintf('%02d',$arr[2]);
         
        //时分秒默认赋值为0；
        $hour = $minute = $second = 0;   
         
        //转换成时间戳
        $strap = mktime($hour,$minute,$second,$month,$day,$year);
         
        //获取数字型星期几
        $number_wk=date("w",$strap);
         
        //自定义星期数组
        $weekArr=array("星期日","星期一","星期二","星期三","星期四","星期五","星期六");
         
        //获取数字对应的星期
        return $weekArr[$number_wk];
    }
     
    //测试
    $date="2016-08-20";
    echo get_week($date);
    //星期六